This invention relates to an improved filter for use in high pressure separating presses, e.g. cocoa presses. Known filters contain metal screen components consisting of one or more plates of twilled gauze made from steel wire, preferably chromium-nickel steel wire. The mounting of these gauze plates in the front-face of a press platen of a separating press is an act requiring craftsmanship, because the outer rim of the gauze plate is bent through 90.degree. and then fastened in place, e.g. by pressing a fastening means (e.g. a cord) into a circular recess of the press platen, said recess often having a trapezoidal cross-section. It is unavoidable that the weft threads of the screen component loosen, notably in the zone where the warp threads are in radial or virtually radial direction. This results in the development of weak points in the gauze plates where, in spite of skilled and precise mounting, further damage, e.g. breakage of wires, not infrequently occurs. The warp threads of such gauze plates typically have a diameter between about 0.3 and 0.35 mm and the weft threads have a diameter of about 0.2 mm.
During the operation of the separating presses such high pressures are used that breakage or further breakage of wires may occur at the weak points of the gauze plates. Once a wire is broken somewhere along its length, the protruding end can become trapped in the press cake and consequently be broken off when the press cake is removed. If this happens in the case of a cocoa press or a press for food or feed material, this can lead to pieces of wire getting into the press cake, resulting in damage to the mill or to customer complaints.
The occurrence of broken wires, and also of excessive deformation of the gauze plates, must be checked for by regular inspection. As soon as this is found to occur, the filter must be replaced. The time during which the filter screen serves before it must be removed is called the useful life of the screen component.